Pneumatic pressure control device

ABSTRACT

A pressure control means comprising a jet pump ( 1 ) whose pressure state in a branch flow duct ( 4 ) may be changed by means of a choke ( 6 ), which influences the spent air flow from the jet pump ( 1 ). This renders possible a rapid and stepless variation of the pressure state in the branch flow duct ( 4 ).

FIELD OF THE INVENTION

The invention relates to a pneumatic pressure control means for theproduction of at least two different pressures in a load line by the useof adjustment means.

BACKGROUND OF THE INVENTION

Conventionally different pressures are made available in a load line byswitching over a three way valve between two supply lines, which carrythe desired pressures.

Furthermore it is a customary practice to utilize jet pumps to producevacuum, in the case of which a jet tube nozzle carrying a fluid undergage pressure injects such fluid into a principal flow duct. In thetransition zone between the jet nozzle and the principal flow duct abranch flow duct is provided in which vacuum is produced owing to thehigh flow speed of the medium.

SUMMARY OF THE INVENTION

One object of the invention is to provide a simple means by whichpressures with different levels may be produced in a connected loadline.

The pressure differences required in the branch flow duct are producedby influencing the principal flow without a valve being necessary forthis purpose. Since the back pressure is influenced without makingphysical contact, use is more particularly advantageous in cases wherefrequent and rapid changes in pressure are required. The back pressuremeans may for example be in the form of a counter pressure nozzledirected against the outlet flow opening, whose flow rate may bechanged. The back pressure means may furthermore be in the form ofslides able to be moved, for example perpendicularly to the principalflow duct. A particular advantage of the invention is that only onesupply duct is required, which may be more readily laid and connected asa double line in a restricted space. This means that it is possible toarrange the control means close to the load so that the change inpressure may take place particularly rapidly.

The influence on flow may be for example so set that the flow speed inthe principal duct is reduced and the vacuum effective in the branchflow duct is eliminated or, dependent on the size of the back pressure,is converted into gage pressure. In this respect it is an advantage forthe principal flow duct to be designed so that it flares like a trumpettoward the outlet opening in order to achieve flow with a minimumresistance. The back pressure means may, for example, be usch as to beable to be set in only two functional positions so that the pressurecontrol means is merely effective as a sort of two way valve. It ishowever also possible to provide a multi-stage setting or adjustment soas to have any desired number of output pressures.

A baffle-like choke may be actuated by a shifting movement toward theoutlet flow opening or athwart same without any mutual contactoccurring. This simplifies the mechanical actuation and function of thepneumatic operations and may take place without mechanical wear, thechoke being mechanically simple in design and as regards its guidemeans.

Therefore, as a result of the present invention, it is possible toregulate the pressures required in fine steps and to adapt same tovarious different conditions of use.

A displacement measuring means further renders possible a rapid movementof the choke into a predetermined position with a correspondinglydefined pressure in the load line.

A pressure sensor and a control make it possible for the pressure in theload line to be set precisely and contact in a manner independent fromthe flow rate.

Linear drives produce a high hold and setting force so that a rapidsetting action on the choke and reliable holding in the set position ispossible. A moving coil may for example be designed like a loudspeakerand be coupled with a diaphragm sealing off the coil space so that samemay be filled with a damping liquid.

In the following the invention will be described in detail withreference to the embodiments illustrated in accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal section taken through a pneumatic pressurecontrol means.

FIG. 2 shows pressure control means in another functional position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1 the reader will see a pneumatic pressure control means in anaxial longitudinal section. A jet pump 1 possesses a jet nozzle 2connected with a gage pressure line and directed toward a principal flowduct 3, which is designed as a sort of venturi nozzle. In the transitionzone between the jet nozzle 2 and the principal flow duct 3 a branchflow duct 4 branches off perpendicularly to the principal flow duct 3,such branch duct flaring out in a trumpet-like form toward an outletflow opening 5. The branch duct opens into a spent air chamber, whichthe medium leaves through a muffler 14 out into the surroundings. A loadline 7 is connected with the branch flow duct 4.

A choke 6 is located at some distance from the outlet flow opening 5,which substantially prevents any back pressure in the exiting spent air.In the vicinity of the jet nozzle 2 the flow speed is so high that herea vacuum pressure develops. This vacuum pressure zone extends in thebranch flow duct 4 and in the load line 7. The choke 6 is attached to adrive element, such as an electromagnetic actuator 8 which is operatedin the axial direction by means of a control drive, such as anelectrical coil 9 against the direction of the jet of exiting medium. Adisplacement measuring means 8 a renders possible a rapid movement ofthe choke 6 into a predetermined position with a correspondingly definedpressure in the load line.

A pressure sensor 10 measures the pressure in the branch flow duct 4 andis connected by way of a data line 13 with an electrical controller 12which is connected with the coil 9. Dependent on the amperage suppliedby way of line 13 the inductivity of the coil will be changed togetherwith the position of the electromagnetic actuator 8 with the choke 6.

FIG. 2 shows the baffle-like choke 6 in one position of switching, inwhich the distance from the outlet flow opening 5 is substantiallyreduced. The spent air is now not able to freely flow out and is subjectto such a strong back pressure in the principal flow duct 3 that a gagepressure results in the branch flow duct 4.

What is claimed is:
 1. A pneumatic pressure control means for producingat least two different pressures in a load line, said pneumatic pressurecontrol means including a jet pump comprising: a branch flow ductconnected to the load line; a principal flow duct communicating at oneend with said branch flow duct and having an outlet flow opening at anopposite end thereof; an adjustable back pressure means adjacent saidoutlet flow opening, said adjustable back pressure means influencing apneumatic flow through said principal flow duct such that a pneumaticpressure in said branch flow duct may be changed; a pressure sensor incommunication with said branch flow duct for measuring the pressuretherein and generating a pressure signal based on said measuredpressure; and a controller connected to said pressure sensor and saidadjustable back pressure means, said controller receiving said pressuresignal from said pressure sensor and controlling said adjustable backpressure means based on said received signal.
 2. A pressure controlmeans as defined in claim 1, wherein said back pressure means comprisesan adjustable choke, said choke being adjustable to change a flowcross-section of said outlet flow opening of said principal flow duct.3. A pressure control means as defined in claim 2, wherein saidadjustable choke is in the form of a baffle and is adjustable to bemoved into a position in front of said outlet flow opening.
 4. Apressure control means as defined in claim 3, wherein said adjustablechoke is adjustable to be moved in an output flow direction toward saidoutlet flow opening.
 5. A pressure control means as defined in claim 3,further comprising a drive element and a control drive for moving saiddrive element, said adjustable choke being attached to said driveelement.
 6. A pressure control means as defined in claim 5, wherein saidcontrol drive comprises a displacement measuring means.
 7. A pressurecontrol means as defined in claim 5, wherein said controller isconnected to said pressure sensor and said control drive, saidcontroller evaluating said pressure signal from said pressure sensor andcontrolling said control drive based on said received signal.
 8. Apressure control means as defined in claim 5, wherein said drive elementcomprises a moving coil, said choke acting attached to said moving coil.9. A pressure control means as defined in claim 5, wherein said driveelement comprises an electromagnetic actuator having a moving magnet,said choke being attached to said moving magnet.
 10. A pressure controlmeans as defined in claim 5, wherein said drive element comprises alinear motor having a moving part, said choke being attached to saidmoving part.